In the past, as one example of a starter of this type which housed a planetary reduction gear, there was the device shown in FIG. 1. In this figure, 100 is the armature of a direct current motor which is constituted by the following components. 101 is an armature core and 102 is an armature rotating shaft on the middle of which the armature core 101 is mounted. A commutator 103 fits on the rear portion of the armature 100. An armature coil 104 which is wound on the armature core 101 is connected to the commutator 103. 105 is brushes which are in contact with the commutator 103 and a holder which is connected to a rear bracket 107 by a bolt 106. 108 is a bearing which journals the rear end portion of the armature rotating shaft 102 and which is inserted into a recess in the rear bracket 107. 109 is a yoke of the direct current motor. A plurality of permanent magnets 109a which generate a magnetic field in the armature 100 are secured to its inner peripheral surface. A front bracket 111 in which is fit an internal gear 110 which constitutes a planetary reduction gear is mounted on the end surface of the yoke 109 as shown in the figure. A spur gear 112 is formed on the front end of the armature rotating shaft 102. Both it and the internal gear 110 mesh with a plurality of planetary gears 113. 114 indicates bearings which are mounted on the inner peripheral surfaces of the planetary gears 113 and which are journalled on supports pins 115. 116 is a flange to which the support pins 115 are secured. It constitutes an arm of the planetary reduction gear and is secured to an output rotating shaft 117. 118 is a sleeve bearing which fits into the inner periphery of a protrusion of the internal gear 110 and which journals the output rotating shaft 117. 119 is a sleeve bearing which fits into a recess in the rear portion of the output rotating shaft 117 and which journals the front end of the armature rotating shaft 102. 120 is a steel ball which is disposed between the ends of the armature rotating shaft 102 and the output rotating shaft 117 and which has the function of bearing thrusts.
121 indicates helical splines which are formed on the outside of the midportion of the output rotating shaft 117. An overrunning clutch 122 engages therewith so as to be able to slide back and forth. 123 is a stopper which is disposed on the front end of the output rotating shaft 117 and which restricts the axial movement of a pinion 124 which is connected to the overrunning clutch 122. 125 is a sleeve bearing which is mounted on the inner surface of the front end of the front bracket 111 and which journals the front end of the output rotating shaft 117. 126 is a molded resin-based plastic lever which has a rotating shaft 126a at its midportion. As shown in the drawing, one end is connected to a plunger 128 of a solenoid switch 127 and the other end fits around the outside of the overrunning clutch 122. 129 is a movable contact which is mounted on a rod 131 through an electrically insulating member 130, the rod 131 being inserted into a core 132 and being slidable back and forth therein. 133 is a stationary contact which is secured to an electrically insulating member in the form of a cap 135 by a nut 134. 136 is an exciting coil which activates the plunger 128. It is wound around a molded plastic bobbin 137 and is housed inside a case 138. 139 is a lead wire which is connected to the stationary contact 133 and to the brushes of the brushes and holder 105.
Next, the operation will be explained. When an unillustrated starter switch is closed to cause current to flow through the exciting coil 136 of the solenoid switch 127, the plunger 128 is activated and moves backwards, pushing the rod 131 backwards and making the movable contact 129 and the stationary contact 133 contact one another. As a result, current is supplied from the stationary contact 133 to the armature 100 by the brushes and holder 105 via the lead wire 139, and the armature 100 generates rotational force. The rotation of the armature 100 is transmitted from the spur gear 112 to the planetary gears 113, and the rotation is transmitted to the overrunning clutch 122 while being reduced in speed by the planetary reduction gear. At this time, the pinion 124 which engages with the overrunning clutch 122 is made to rotate.
On the other hand, the force of the plunger 128 which is activated in the above manner causes the lever 126 to rotate in the counterclockwise direction about the rotating shaft 126a and slide the overrunning clutch 122 and the pinion 124 forward in the axial direction. As a result, the pinion 124 is brought into engagement with a ring gear which is secured to a flywheel which is mounted on the crankshaft of an unillustrated engine.
After the engine is started, the overrunning clutch 122 separated from the pinion 124 due to the rotation of the engine with respect to the pinion 124, and the pinion 124 will perform idle rotation.
As a conventional engine starter is constructed in the above-described manner, the solenoid switch and the direct current motor have their shafts arranged in parallel, so when the starter is mounted on an engine, it is necessary to ensure space for the solenoid switch in either the engine or in the portion of the side of the vehicle into which the engine fits. This creates problems such as restrictions on the engine layout in the vehicle. In addition, there was the problem that in order to avoid interference between the front end of the front bracket and a member such as a flywheel within the engine transmission housing, the shape of the flywheel was limited.
This invention was made in order to solve the above-described problems, and its object is to provide an engine starter in which a solenoid switch and a motor can be coaxially disposed, in which the bearing for the output rotating shaft is cantilevered as seen from the pinion, and which is easy to mount on an engine.